Accounting Capital budgeting?

ABC Company is considering two long-term investment proposals. The initial outlay for Project L is $75,000, salvage value for the project is $25,000, and the expected after tax cash returns (including the salvage value) are given below throughout its expected 4 year useful life. Project M, if selected will have to be replaced after 5 years and cost $95,000. It will have no salvage value. Its expected cash inflows are also shown below.

YEAR PROJECT M ----- PROJECT L
1 $25,000 ------- 31,000
2 30,000 ------- 35,000
3 25,000 ------- 40,000
4 30,000 ------- 23,000
5 0 -------- 15,000

What is the payback period (to the nearest tenth of a year) for each project? Using the payback method as the selection criteria, which project would you select

This sounds like a textbook problems you must do yourself so I will not give you the answer. I will ask, why are they still teaching payback instead of discounted cash flow/ net present value and internal rate of return